Due to the recent increase in high definition video contents, the need for a video codec having a higher coding efficiency than a video codec according to the related art such as MPEG-4 H.264/MPEG-4 advanced video coding (AVC) is growing.
Motion compensation is a technique used in removing temporal redundancy in a video signal. By motion compensation, a residual signal which is a difference between an original signal and a reference signal indicated by a motion vector is transmitted to thereby increase a compression efficiency of video coding. In general, a motion vector and a residual value of each block are transmitted to a decoder's end as a result of encoding of each block obtained by motion compensation. Since motion vectors of the respective blocks occupy a considerable portion of an encoded bitstream, information about the motion vectors allocated to the respective blocks is to be reduced in order to increase a compression efficiency.
To reduce a transmission overhead according to encoding of a motion vector, in MPEG-2 codec according to the related art, a motion vector of a previous block is used as a motion vector predictor of a current block, and in codecs such as MPEG-4 H.264/MPEG-4 AVC, a median of motion vectors of previously encoded blocks that are adjacent to a current block on the left, upper, and above right sides is used as a motion vector predictor.